Re: [PATCH net v2] Revert "virtio-net: ethtool configurable RXCSUM"

["Michael S. Tsirkin" <mst@redhat.com>]

On Tue, Oct 20, 2020 at 02:13:06PM +0800, Jason Wang wrote:
> 
> On 2020/10/20 上午1:32, Michael S. Tsirkin wrote:
> > This reverts commit 3618ad2a7c0e78e4258386394d5d5f92a3dbccf8.
> > 
> > When the device does not have a control vq (e.g. when using a
> > version of QEMU based on upstream v0.10 or older, or when specifying
> > ctrl_vq=off,ctrl_rx=off,ctrl_vlan=off,ctrl_rx_extra=off,ctrl_mac_addr=off
> > for the device on the QEMU command line), that commit causes a crash:
> > 
> > [   72.229171] kernel BUG at drivers/net/virtio_net.c:1667!
> > [   72.230266] invalid opcode: 0000 [#1] PREEMPT SMP
> > [   72.231172] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.9.0-rc8-02934-g3618ad2a7c0e7 #1
> > [   72.231172] EIP: virtnet_send_command+0x120/0x140
> > [   72.231172] Code: 00 0f 94 c0 8b 7d f0 65 33 3d 14 00 00 00 75 1c 8d 65 f4 5b 5e 5f 5d c3 66 90 be 01 00 00 00 e9 6e ff ff ff 8d b6 00
> > +00 00 00 <0f> 0b e8 d9 bb 82 00 eb 17 8d b4 26 00 00 00 00 8d b4 26 00 00 00
> > [   72.231172] EAX: 0000000d EBX: f72895c0 ECX: 00000017 EDX: 00000011
> > [   72.231172] ESI: f7197800 EDI: ed69bd00 EBP: ed69bcf4 ESP: ed69bc98
> > [   72.231172] DS: 007b ES: 007b FS: 00d8 GS: 00e0 SS: 0068 EFLAGS: 00010246
> > [   72.231172] CR0: 80050033 CR2: 00000000 CR3: 02c84000 CR4: 000406f0
> > [   72.231172] Call Trace:
> > [   72.231172]  ? __virt_addr_valid+0x45/0x60
> > [   72.231172]  ? ___cache_free+0x51f/0x760
> > [   72.231172]  ? kobject_uevent_env+0xf4/0x560
> > [   72.231172]  virtnet_set_guest_offloads+0x4d/0x80
> > [   72.231172]  virtnet_set_features+0x85/0x120
> > [   72.231172]  ? virtnet_set_guest_offloads+0x80/0x80
> > [   72.231172]  __netdev_update_features+0x27a/0x8e0
> > [   72.231172]  ? kobject_uevent+0xa/0x20
> > [   72.231172]  ? netdev_register_kobject+0x12c/0x160
> > [   72.231172]  register_netdevice+0x4fe/0x740
> > [   72.231172]  register_netdev+0x1c/0x40
> > [   72.231172]  virtnet_probe+0x728/0xb60
> > [   72.231172]  ? _raw_spin_unlock+0x1d/0x40
> > [   72.231172]  ? virtio_vdpa_get_status+0x1c/0x20
> > [   72.231172]  virtio_dev_probe+0x1c6/0x271
> > [   72.231172]  really_probe+0x195/0x2e0
> > [   72.231172]  driver_probe_device+0x26/0x60
> > [   72.231172]  device_driver_attach+0x49/0x60
> > [   72.231172]  __driver_attach+0x46/0xc0
> > [   72.231172]  ? device_driver_attach+0x60/0x60
> > [   72.231172]  bus_add_driver+0x197/0x1c0
> > [   72.231172]  driver_register+0x66/0xc0
> > [   72.231172]  register_virtio_driver+0x1b/0x40
> > [   72.231172]  virtio_net_driver_init+0x61/0x86
> > [   72.231172]  ? veth_init+0x14/0x14
> > [   72.231172]  do_one_initcall+0x76/0x2e4
> > [   72.231172]  ? rdinit_setup+0x2a/0x2a
> > [   72.231172]  do_initcalls+0xb2/0xd5
> > [   72.231172]  kernel_init_freeable+0x14f/0x179
> > [   72.231172]  ? rest_init+0x100/0x100
> > [   72.231172]  kernel_init+0xd/0xe0
> > [   72.231172]  ret_from_fork+0x1c/0x30
> > [   72.231172] Modules linked in:
> > [   72.269563] ---[ end trace a6ebc4afea0e6cb1 ]---
> > 
> > The reason is that virtnet_set_features now calls virtnet_set_guest_offloads
> > unconditionally, it used to only call it when there is something
> > to configure.
> > 
> > If device does not have a control vq, everything breaks.
> > 
> > Looking at this some more, I noticed that it's not really checking the
> > hardware too much. E.g.
> > 
> >          if ((dev->features ^ features) & NETIF_F_LRO) {
> >                  if (features & NETIF_F_LRO)
> >                          offloads |= GUEST_OFFLOAD_LRO_MASK &
> >                                      vi->guest_offloads_capable;
> >                  else
> >                          offloads &= ~GUEST_OFFLOAD_LRO_MASK;
> >          }
> > 
> > and
> > 
> >                                  (1ULL << VIRTIO_NET_F_GUEST_TSO6) | \
> >                                  (1ULL << VIRTIO_NET_F_GUEST_ECN)  | \
> >                                  (1ULL << VIRTIO_NET_F_GUEST_UFO))
> > 
> > But there's no guarantee that e.g. VIRTIO_NET_F_GUEST_TSO6 is set.
> > 
> > If it isn't command should not send it.
> > 
> > Further
> > 
> > static int virtnet_set_features(struct net_device *dev,
> >                                  netdev_features_t features)
> > {
> >          struct virtnet_info *vi = netdev_priv(dev);
> >          u64 offloads = vi->guest_offloads;
> > 
> > seems wrong since guest_offloads is zero initialized,
> 
> 
> I'm not sure I get here.
> 
> Did you mean vi->guest_offloads?
> 
> We initialize it during probe
> 
>     for (i = 0; i < ARRAY_SIZE(guest_offloads); i++)
>         if (virtio_has_feature(vi->vdev, guest_offloads[i]))
>             set_bit(guest_offloads[i], &vi->guest_offloads);
> 

Good point, will drop this part.


> > it does not reflect the state after reset which comes from
> > the features.
> > 
> > Revert the original commit for now.
> > 
> > Cc: Tonghao Zhang <xiangxia.m.yue@gmail.com>
> > Cc: Willem de Bruijn <willemb@google.com>
> > Fixes: 3618ad2a7c0e7 ("virtio-net: ethtool configurable RXCSUM")
> > Reported-by: kernel test robot <lkp@intel.com>
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> > 
> > changes from v1:
> > 	- clarify how to reproduce the bug in the log
> > 
> > 
> >   drivers/net/virtio_net.c | 50 +++++++++++-----------------------------
> >   1 file changed, 13 insertions(+), 37 deletions(-)
> > 
> > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> > index d2d2c4a53cf2..21b71148c532 100644
> > --- a/drivers/net/virtio_net.c
> > +++ b/drivers/net/virtio_net.c
> > @@ -68,8 +68,6 @@ static const unsigned long guest_offloads[] = {
> >   				(1ULL << VIRTIO_NET_F_GUEST_ECN)  | \
> >   				(1ULL << VIRTIO_NET_F_GUEST_UFO))
> > -#define GUEST_OFFLOAD_CSUM_MASK (1ULL << VIRTIO_NET_F_GUEST_CSUM)
> > -
> >   struct virtnet_stat_desc {
> >   	char desc[ETH_GSTRING_LEN];
> >   	size_t offset;
> > @@ -2524,48 +2522,29 @@ static int virtnet_get_phys_port_name(struct net_device *dev, char *buf,
> >   	return 0;
> >   }
> > -static netdev_features_t virtnet_fix_features(struct net_device *netdev,
> > -					      netdev_features_t features)
> > -{
> > -	/* If Rx checksum is disabled, LRO should also be disabled. */
> > -	if (!(features & NETIF_F_RXCSUM))
> > -		features &= ~NETIF_F_LRO;
> > -
> > -	return features;
> > -}
> > -
> >   static int virtnet_set_features(struct net_device *dev,
> >   				netdev_features_t features)
> >   {
> >   	struct virtnet_info *vi = netdev_priv(dev);
> > -	u64 offloads = vi->guest_offloads;
> > +	u64 offloads;
> >   	int err;
> > -	/* Don't allow configuration while XDP is active. */
> > -	if (vi->xdp_queue_pairs)
> > -		return -EBUSY;
> > -
> >   	if ((dev->features ^ features) & NETIF_F_LRO) {
> > +		if (vi->xdp_queue_pairs)
> > +			return -EBUSY;
> > +
> >   		if (features & NETIF_F_LRO)
> > -			offloads |= GUEST_OFFLOAD_LRO_MASK &
> > -				    vi->guest_offloads_capable;
> > +			offloads = vi->guest_offloads_capable;
> >   		else
> > -			offloads &= ~GUEST_OFFLOAD_LRO_MASK;
> > +			offloads = vi->guest_offloads_capable &
> > +				   ~GUEST_OFFLOAD_LRO_MASK;
> > +
> > +		err = virtnet_set_guest_offloads(vi, offloads);
> > +		if (err)
> > +			return err;
> > +		vi->guest_offloads = offloads;
> >   	}
> > -	if ((dev->features ^ features) & NETIF_F_RXCSUM) {
> > -		if (features & NETIF_F_RXCSUM)
> > -			offloads |= GUEST_OFFLOAD_CSUM_MASK &
> > -				    vi->guest_offloads_capable;
> > -		else
> > -			offloads &= ~GUEST_OFFLOAD_CSUM_MASK;
> > -	}
> > -
> > -	err = virtnet_set_guest_offloads(vi, offloads);
> > -	if (err)
> > -		return err;
> > -
> > -	vi->guest_offloads = offloads;
> >   	return 0;
> >   }
> > @@ -2584,7 +2563,6 @@ static const struct net_device_ops virtnet_netdev = {
> >   	.ndo_features_check	= passthru_features_check,
> >   	.ndo_get_phys_port_name	= virtnet_get_phys_port_name,
> >   	.ndo_set_features	= virtnet_set_features,
> > -	.ndo_fix_features	= virtnet_fix_features,
> >   };
> >   static void virtnet_config_changed_work(struct work_struct *work)
> > @@ -3035,10 +3013,8 @@ static int virtnet_probe(struct virtio_device *vdev)
> >   	if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO4) ||
> >   	    virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_TSO6))
> >   		dev->features |= NETIF_F_LRO;
> > -	if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS)) {
> > -		dev->hw_features |= NETIF_F_RXCSUM;
> > +	if (virtio_has_feature(vdev, VIRTIO_NET_F_CTRL_GUEST_OFFLOADS))
> >   		dev->hw_features |= NETIF_F_LRO;
> > -	}
> >   	dev->vlan_features = dev->features;